Casting process



June 7, 1966 e. w. BELCHER CASTING PROCESS Filed June 11, 1964 1 I 52 50g5 Z6 Z5 2'0 76 INVENTOR.

GEORGE W. BELCHER A TTOPNEV Jig,

United States Patent This application is a continuation-in-part of mycopending application, Serial No. 147,549, filed October 25, 1961, nowabandoned.

The present invention relates generally to a process for casting metalsand, more particularly, to casting process wherein a shell of castingslag is formed on the inner walls of the casting form.

Heretofore, a variety of casting processes have been proposed wherein ashell of casting slag is formed on the inner Walls of the casting moldprior to or simultaneously with the pouring of the metal to be cast. Themain purpose'of the shell of casting slag is to produce a smooth ingotsurface substantially free of imperfections which deleteriously aflf'ectWorked articles formed therefrom.

I. The smooth ingot surface is produced by employing a casting slaghaving a melting point below the melting point of the metal being castso that the molten metal freezes in contact with a fluid shell ratherthan a solid casting mold. Also, when the shell is pre-formed on theentire inner surface of the mold, splashings from the molten metal beingpoured melt the inner surface of the shell at the point of impingementand fall back into the pool of molten metal rather than clinging to themold wall. As a result, the splashings do not form scabs and v sliverson the ingot surface. Typical examples of casting processes wherein ashell of casting slag is employed are described in more detail in U.S.Patent No. 2,631,344 to Kennedy and U.S. Patent No. 2,443,394 to Dunn etal.

As mentioned in the Kennedy patent, the shell of casting slag can beformed on the inner walls of the casting mold in various ways. Forexample, the molten metal to be cast may be poured into a mold partiallyfilled with molten casting slag so that a layer of the molten slag riseson top of the pool of molten metal and forms a shell on successive zonesof the mold wall. Alternatively, the entire inner surface of the moldmay be covered with a shell of casting slag prior to the pouring of themetal by completely filling the mold with molten casting slag andallowing it to stand until a shell of the desired thickness hassolidified on the mold walls.; However, in such processes the castingslag must be pro-melted, poured into the casting mold, and allowed tostand before the.

metal can be poured. Also, the molten pool of casting slag employed insuch processes permits very little control of the dimensions of theshell.

Another type of process, intended mainly to increase the life of molds,involves providing a mold with a coating of a refractory materialWhiCh'Wlll present a smooth generally glass-like surface to the moltenmetal. Such coatings or protective linings can be applied by flamespraying refractory particles onto the interior walls of a mold to forma continuous shell of solidrefraotory in which to cast the metal.Because of the differences in coefiicients of expansion of the moldwalls and such refractory coatings, the glass-like lining will oftenbreak 3,254,380 Patented June 7, 1966 parent from the followingdescription and appended claims.

In the drawings:

FIG. 1 is a perspective view of a preferred flame torch for carrying outthe inventive process; and

FIG. 2 is aview in side elevation of the torch of FIG. 1.

In accordance with the present invention, a process for casting metal ina mold is provided comprising directing a stream of particulated castingslag material through a flame to partially fuse the slag particles anddirecting the stream of partially fused slag particles onto the moldWalls for adherence to the mold walls and to each other to form a liningof surface-bonded slag particles on the walls of the mold, pouringmolten metal into the so-lined mold and allowing the heat of the moltenmetal to fuse the slag lining forming a shell of fluid casting slagbetween the metal body and the walls of the mold,-and solidifying themetal body in the mold-supported shell of casting slag.

The above described process provides a simple method ing molds with themolten slag. By providing a mold with a lining of surface-bonded slagparticles and casting metal therein, the shell of fluid casting slag isformed in situ. The application of only partially-fused, i.e., onlysurface-melted, particles to the mold wall results in the deposition ofa semi-porous, surface-bonded slag particle structure. This semi-porousstructure of surfacebonded slag particles is more resistant to thethermal shock and expansion caused bythe pouring of the intensely hotmolten metal into the mold. The application of completely fused orsoftened slag particles or droplets would result in the formation of afused layer of slag on the mold walls which would solidify into a solidsheet of slag. Such a solid sheet of slag does not have the necessarythermal shock resistance to resist massive spalling when hot metal ispoured into the mold.

The slag lining deposited according to this inventionhas some degree ofporosity, i.e., voids are interspersed between many of thesurface-bonded slag particles. This structure which is said to besemi-porous because the voids are not completely continuous, gives thelining an ability to absorb the expansive forces caused by the hotmetal. The slag lining produced by this process thus can remainsubstantially integral until the rising surface a of the molten metalreaches successive levels of the slag lining, which is then melted bycontact with the hot metal to form the desired shell of fluid castingslag around the body of metal.

Metal splashings which occur during pouring only adhere to and pull awaya small portion of the relatively weakly bonded slag particle lining anddo not leave large unprotected areas on the mold wall. The lowdensitysurface-bonded slag material which is pulled 01f the mold walls willrise to the surface of the molten metal and not form inclusions therein.

The semi-porous lining also allows for the escape of gases evolved inthe casting operation which otherwise might be trapped in the metalbody. The gases are able to pass vertically through the semi-porouslining a dis- (3 tance above the surface of the molten metal and thenceinto the center of the mold cavity as yet unoccuppied by metal fromwhence they can escape to the atmosphere.

The process of this invention allows for the forma- ;ion of the silicateslag lining in mold walls without the use of harmful binders to hold theslag particles to :he mold wall. Such binders tend to generate gaseswhen iubjected to the heat of the molten metal and tend to :ausespalling of mold linings. The decomposition prodicts of the scorchedbinders may deleteriously affect the :ast metal. In this process bindersare not necessary for be partially fused particles adhere to the moldwalls 1nd to each other to form a semi-porous lining.

The inventive process permits relatively close dimen- ;ional control ofthe slag shell by applying the slag to ;he mold wall in the form of astream of partially molten ilag particles. The slag particles can beapplied in 1 relatively narrow stream, thereby permitting the forma-Lion of sharp corners in the slag shell, and yet a shell )f any desiredthickness can be formed rather rapidly by noving the stream of partiallymolten slag over the nold wall at a relatively high speed. Even in thecase at complex mold shapes, the shell can be made to conform closely tothe shape of the mold. Since only the ;urfaces of the slag particles aremelted, and only enough Jfll'tlClES to form the desired shell, there isno need to nelt a body of slag sufficient to fill all or part of the:asting form. Also, since there is no body of molten ;lag in contactwith the partially molten shell, it solidiies quickly without standingfor a long period.

The casting slag employed in this process should be generally inert tothe metal to be cast and should have t melting point below that of themetal. The casting ilag may for special reasons contain elementsfavorably reactive with the cast body, if they do not otherwiseinterfere with the casting process. The casting slag also pref- :rablyhas a density less than the density of the metal to be cast. Thecompositions of casting slags will vary with :he metal to be cast. Thegeneral composition of the :asting slags include such metallic silicatesas the calcium magnesium-aluminum silicates. The silica content of :hecoating slag should generally be in the range of about 15 percent toabout 55 percent by weight, and pref- :rably in the range 40 to 45percent silica. For example, a. slag suitable for use with 1040 steelcontains 44% silica, 35% calcium oxide, 5% magnesium oxide, 7% :itania,6% calcium fluoride, 1% manganese oxide, 1% ferrous oxide and 1%aluminum oxide. Compositions of some suitable slags for general use withferrous metals given below in Table 1:

The above listed casting slags have melting points of about 1200 C. (A)and about 1l00 C. (B) and can be used for casting carbon steel and otherferrous metals, including most stainless steels. When casting ferrousmetals which contain reactive metals such as titanium, aluminum, andzirconium, an undesirable amountof the reactive metal is lost byreaction with the silica in the shell of casting slag, with acorresponding increase in the amount of silicon in the cast body. Insuch cases it is preferable to use a casting slag having less than 15percent by weight silica. Titanium oxide and/or aluminum oxide may besubstituted for a substantial part of the reduced silica content. Thecomposition of the casting slag could contain oxides of calcium,magnesium, manganese, aluminum, titanium, zirconium, and iron, calciumfluoride and/or sodium-aluminum fluoride and less than 15 percent byweight silica. Suitable compositions of these low silica casting slagsare given in Table 2.

TABLE 2 Composition, percent by weight Casting Slag Preferred RangeTypical C C210, 32 t0 35 34 Others- 1 About.

These casting slags have approximate melting points of about 1250 C.(C), about 1325 C. (D), and 1300 C. (B). These slags generally have amajor portion of lime and alumina in their compositions and a silicacontent less than about 15 percent by weight. The above noted low silicacasting slags are useful in casting titanium and aluminum containingsteels, as well as stainless steels in general, and thetitanium-aluminum precipitation hardened nickel and cobalt superalloys.

In regard to casting other non-ferrous metals and alloys the castingslag is generally made chemically inert to the metal to be cast and hasa lower melting point than the metal so that the casting slag is stillfluid after the metal has at least partially solidified. In Table 3 somesuitable slag compositions for casting copper and its alloys are shown:

540 C. (F) and about 830 C. (G).

The slag material is prepared by standard melting techniques and thencrushed into particles for flame spraying. The slag particles should besmall enough to avoid clogging the supply line therefor and to adhere tothe mold Wall when the particles are partially molten. Of course, theslag particles should not have a dimension greater than the desiredshell thickness. A particle size between about 20 and about 300 mesh isgenerally preferred for most applications. The actual particle sizedistribution should be such as to yield the semi-porous lining andshould not contain an excessive amount of fine particles which wouldtend to plug the pores.

The thickness of the shell of casting slag deposited on the mold wallsis determined mainly by the deposition rate of the stream of partiallymolten slag particles and the speed atwhich the stream is moved acrossthe mold wall. The shell should have suflicient thickness to preventpenetration thereof by the molten metal being cast. The shells shouldhave smaller internal dimensions than the external dimensions desired inthe final ingot. The slag which is melted from the shell during thepouring operation rides on the rising pool of metal, thereby isolatingthe metal from the surrounding atmosphere, and allows the ingot tosolidify without any outside contamination. It is usually preferred tohave a slightly greater shell thickness at the bottom of the mold toprovide for the initial impact of the molten metal. Shells of excessivethickness should be avoided, since such shells do not have sufficientbody to withstand the heat shock of the molten metal without spalling.Also, excessive shell thicknesses result in small ingots and mayinterfere with the removal of the ingot from the mold. Preferred shellthicknesses are usually less than about 35 inch.

The inner walls of the shell of casting. slag, i.e., the walls whichcontact the molten metal to be cast, should be at a temperature abovethe temperature of the outer walls of the shell, i.e., the walls whichcontact the casting form. Preferably, the inner walls of the shellshould be at a temperature approaching the melting point of the castingslag so that metal splashings occurring during the pouring operationliquefy the surface of the shell at the point of impingement and are notretained on the inner surface of the shell. Since the melting of theinner surface of the shell causes the splashings to fall back into themolten metal being cast, they do not form scabs and slivers on the ingotsurface. It is also important that the outer walls of the shell be at atemperature sufliciently low to freeze the molten metal so that themolten metal solidifies before coming into contact with the castingform. Since the temperature of the air surrounding the casting mold isnormally considerably below the temperature of the molten metal beingpoured, the desired temperature gradient in the slag shell is usuallyachieved without the use of cooling or heating devices.

The heating means for partially fusing the slag material may be anysuitable heat source which can properly heat the stream of generally gasborne slag particles. Flame and plasma devices are examples of suchmeans although other heating sources are within the scope of thisinvention. The preferred means for melting the surfaces of the slagparticles and applying the slag to the inner walls of the casting moldare flame torches, such as the torches commonly used in the washing,cutting, scarfing, gouging, etc. of cast ingots. A typical flame torchwhich has been used in carrying out the inventive process emits a roundjet of oxygen surrounded by a circle of small flame ets. The finelydivided casting slag particles are fed into the oxygen and flame inlets,whereupon they are discharged with the flame. In order to preventmelting of the mold wall, the distance between the torch and the moldwall must be greater than the distance between the torch and the ingotin a Washing or cutting operation. However, the distance between thetorch and the mold wall must be small enough to cause the partiallymolten slag particles to adhere to the mold wall.

A suitable flame torch for carrying out the inventlv process will now bedescribed in detail by referring to the drawings:

Referring to the drawings, oxygen and suitable fuel gases for formingthe flame jets are fed into the torch 10 through throttle valves 14 and16 in the handle 12 of the torch. The only requirement on the fuel gasis that it burn at a temperature above the melting point of theparticular casting slag being used. A mixture of oxygen and acetylene issuitable for use with most casting slags. Prom throttle valves '14 and:16, the fuel gas mixture is passed through pipe 28 to the head of thetorch and is finally discharged through an annular series of passages 40in a nozzle 32. The fuel gas is ignited as it leaves the passages 40,thus forming an annular arrangement of flame jets 44.

The pressure or velocity of the flame jet is controlled by means of thethrottl valves 14 and 16.

A carrier gas is fed into the torch through a valve 17, which has acontrol lever 18 extending forwardly over the handle '12. The carriergas is preferably oxygen, but may be nitrogen, argon, or any othersuitable gas or gas mixture. Some torches may not even use a carriergas. From valve 17, the carrier gas is passed through pipe 26 to thehead 30 of the torch and is discharged through a passage 42 disposedwithin the annularseries of flame-jet passages 40. The pressure orvelocity of the resulting jet 36 of carrier gas is controlled by meansof lever 18 on the valve 17.

The third inlet to the torch is for the finely divided or powderedcasting slag. The slag is supplied through an inlet tube 20 whichextends alongside th handle 12and leads to a powder valve 21 having anupwardly extending finger piece 22 located in front of the lever 18. Thepowdered slag is forced through the tube 20 by means of compressed air(source not shown); From valv 21, the

' air-borne powdered slag is passed through a pipe 24 to a flat nozzle34, which is connected to the head 30 by means of a clamp 35. Since thetubular nozzle 32 is bent toward the flat nozzle 34, as shown in FIG. 2,the powdered slag stream 38 is discharged at an acute included angleinto the flame jet 44 and the carrier gas jet 36. The flow rate of thepowdered slag is varied by means of the finger piece 22 on the valve 21.

As the powdered slag is discharged into the flame jets and the carriergas, the slag'particles are swept along with the flames and carrier gasand are travelling in the general direction of the flame jets when theyleave the flame jets and strike the mold wall. The degree of meltingeffected in the slag particles as they pass through the flame jet isdetermined mainly by the temperature of the flame jet, the size of theslag particles, and the length of the period of contact between the slagparticles and the flame jet; the period of contact is determined by thevelocity of the stream of powdered slag, the velocity of the flame jetand carrier gas, and the length of the fla-me jet from the point wherethe powdered slag is introduced therein. In operation, one or more ofthe aforementioned variables are adjusted so that the slag particlesremain in contact with the flame jet just long enough to melt thesurfaces of the particles, i.e., to only partially melt the particles.The degree of melting in the slag particles should be just suflicient tocause the particles to adhere to the mold wall and to each other. It isespecially important that the layer of casting slag deposited on themold walls be only partially molten and so form a surface-bonded,semipor-ous layer thereon so that the resulting slag shell willwithstand the heat shock of the molten metal during the pouringoperation. If the slag particles are completely molten so as to form acompletely molten layer of slag on the mold, the resulting slag shell islikely to spall or shatter during the pouring operations.

The torch should be held so that the stream of partially molten slagparticles is directed against the inner walls of the casting form, andthen moved back and forth across the walls while being advanced in adirection parallel to the walls. Generally the walls and floor of themold are covered although in some cases the floor of the mold may becovered with other materials, or left bare. Therefore when it is statedherein that the mold walls are lined with the coating, it is also meantthatthe floor of the mold is coated if desired. It is preferred to applyI the slag stream to the mold in a direction about perpendicular to themold walls. As mentioned above, the distance between the end of thetorch and the mold walls should be great enough to prevent any meltingof the mold but small enough to cause the partially molten slag toadhere to the mold wall. In order to achieve good adhesion of thepartially molten slag particles to the mold and to each other, it isoften desirable to preheat the mold to a temperature of about 500 to 800F. prior to the deposition of the slag.

Although the torch described above is the best mode contemplated by theinventor for carrying out the inventive process, a great variety offlame torches are known in the art and are operable in the presentprocess. For example, the powdered slag can be introduced into the flamejet within the flame-jet nozzle before the fuel gas is ignited. Asmentioned above, the jet of carrier gas provided by the aforedescribedtorch is not required in all torches. The basic requirements for thetorch are that the flame be hot enough to melt the surfaces of the slagparticles and that the slag particles be provided with a sufiicientvelocity to cause them to adhere to the mold walls.

After the deposited layer of casting slag has solidified into a solidshell, which usually occurs almost simultaneously with the deposition,the molten metal may be poured into the shell at a rate such that onlythe inner surface of the shell is melted. In other words, none of themolten metal should come into contact with the mold walls. Since themelting point of the casting slag is always below that of the metalbeing poured, the molten metal always melts some of the slag shell, andthe outer surface of the metal ingot is in contact with molten slag whenit freezes. Also, a portion of the melted slag forms a protective layeron top of the using pool of slag.

In an example of the inventive process, the torch described above wasused to coat the inner walls of a casting mold with a shell of castingslag having approximately the following composition by weight:

Percent Silica 44 Calcium oxide 35 Magnesium oxide Titania 7 Calciumfluoride 6 Manganese oxide 1 Ferrous oxide 1 Aluminum oxide 1 Themelting point of the casting slag was about 1200 C. and the size of theslag particles fed into thetorch was less than 48 mesh, about 85% of theslag particles being between 100 and 300 mesh. The metal to be cast was1040 steel. The fuel gas was a mixture of oxygen and acetylene and wasfed into ten flame-jet passages (number 56 drill holes) at a pressure ofabout 12 psi. The carrying gas was oxygen and was discharged through aAt-inch central orifice at a pressure of about 90 psi. The powdered slagwas discharged into the flame jets through a /s-inch by l -inch nozzleby means of compressed air (5 p.s.i.) The angl between the slag nozzleand the flame jet was about 30. The powdered slag was swept into thepath of the flame jets and carrying gas and was travelling at a velocityof about 300 feet per second in the general direction of the flame jetswhen it struck the mold wall. The temperature of the flame jet was about5400 F., and the distance between the tip of the flame jet and the moldwall, was maintained between 4 and 8 inches. This distance wassufficient to cause the slag particles to adhere to the mold wallwithout melting the mold. The direction of the stream of partiallymolten casting slag was substantially perpendicular to the mold wall.The rate of deposition of casting slag was about 15 pounds per hour, andthe torch was moved back and forth across the mold wall at a speedsuflicient to form a shell thickness between 1A2 and inch. The partiallymolten slag solidified within a few seconds after it was deposited.After the entire inner surface of the mold had been coated with theslag, the molten 1040 steel was poured into the mold at a rise rate ofabout 45 inches per minute. The mold opening was about four inchessquare. After the ingot had solidified, it was removed from the mold andthe slag envelope removed therefrom. The surface of the ingotwassubstantially free of scabs and other defects and was in conditionfor rolling.

While various specific embodiments of the present invention have beenillustrated and described herein, it is not intended to limit theinvention to any of the details herein shown, but only as set forth inthe appended claims.

While the process of this invention has been described herein in regardto casting ingots in permanent molds, the use of the term molds hereinapplies also to molds used for foundry casting in general, pressurecasting, blow mold castings, lost wax castings, etc., both in permanentand temporary molds, and in general to whatever metal casting operationin which fluid mold casting is operable.

What is claimed is:

1. Process for casting metal in a fluid slag casting mold comprisingheating a stream of particulated casting slag material to partially fusethe slag particles and directing the stream of partially fused slagparticles onto the walls of a mold for adherence to the mold walls andto each other to form a semi-porous lining of surfacebonded slagparticles on the walls of the mold, pouring molten metal into theso-lined mold and allowing the heat of the molten metal to fuse the slaglining forming a shell of fluid casting slag between the metal body andthe walls of the mold, and solidifying the metal body in themold-supported shell of casting slag.

2. Process for casting metal in a fluid slag casting mold comprisingdirecting a stream of particulated cast ing slag material through aflame to partially fuse the slag particles and directing the stream ofpartially fused slag particles onto the walls of a mold for adherence tothe mold walls and to each other to form a semi-porous lining ofsurface-bonded slag particles on the walls of the mold, pouring moltenmetal into the so-lined mold and allowing the heat of the molten metalto fuse the slag lining forming a shell of fluid casting slag betweenthe metal body and the walls of the mold, and solidifying the metal bodyin the mold-supported shell of casting slag.

3. Process for casting metal in a fluid slag casting mold comprisingdirecting a stream of particulated silicate casting slag materialthrough a flame to partially fuse the slag particles and directing thestream of partially fused slag particles onto the walls of a mold foradherence to the mold walls and to each other to form a semi-porouslining of surface-bonded slag particles on the walls of the mold,pouring molten metal into the so-lined mold and allowing the heat of themolten metal to fuse the slag lining forming a shell of fluid silicatecasting slag between the metal body and the walls of the mold, andsolidifying the metal body in the mold-supported shell of casting slag.

4. Process for casting metal in a fluid slag casting mold comprisingdirecting a stream of particulated casting slag material through a flameto partially fuse the slag particles and directing the stream ofpartially fused slag particles onto the walls of a mold for adherence tothe mold walls and to each other to form a semi-porous lining ofsurface-bonded slag particles on the walls of the mold, continuing theapplication of partially fused slag particles until the thickness of thelining is between 4 -inch and As-inch, pouring molten metal into theso-lined mold and allowing the heat of the molten metal to fuse the slaglining forming a shell of fluid casting slag between the metal body andthe walls of the mold, and solidifying the metal body in themold-supported shell of casting slag.

5. Process for casting metal in a fluid slag casting mold comprisingdirecting a stream of particulated casting slag material through a flameto partially fuse the slag particles and directing the stream ofpartially fused slag particles onto the walls of a mold for adherence tothe mold walls and to each other to form a semi-porous lining ofsurface-bonded slag particles on the walls of the mold, pouring moltenmetal into the so-lined mold and allowing the heat of the molten metalto fuse the slag lining forming a shell of fluid casting slag betweenthe metal body and the walls of the mold, and solidifying the metal bodyin the mold-supported shell of casting slag, said casting slag materialbeing a particulated slag composition comprising silicates of calcium,magnesium and aluminum.

6. Process for casting metal in a fluid slag casting mold comprisingdirecting a stream of particulated casting slag material through aflame, maintaining the flame temperature and residence time of saidparticles in said flame at values to partially fused said particles,directing the stream of partially fused slag particles onto the walls ofa mold for adherence thereto and to each other to form a semi-porouslining of surface-bonded slag particles on fuse the slag lining forminga shell of fluid casting slag' between the metal body and the Walls ofth mold, and solidifying the metal body in the mold-supported shell ofcasting slag.

7. Process for casting metal in a fluid slag casting mold comprisingdirecting a stream of particulated silicate casting slag materialthrough a flame, maintaining the flame temperature and residence time ofsaid particles in said flame at values to heat the surfaces of saidparticles to their fusion temperature, directing the stream of hotparticles onto the walls of a mold for adherence thereto and to eachother to form a semi-porous lining of surfacebonded slag particles onthe mold walls, pouring molten metal into the so-lined mold and allowingthe heat of the molten metal to fuse the slag lining forming a shell offluid casting slag between the metal body and the walls of the mold, andsolidifying the metal body in the moldsupported shell of casting slag.

8. Process in accordance with claim 7 wherein the lining ofsurface-bonded casting slag particles is between and A -inches thick.

9. Process for casting ferrous metal in a fluid slag casting moldcomprising directing a stream of particulated casting slag materialthrough a flame, said slag material containing from about 15 to about 55percent by weight 7 silica and having a melting temperature less thanthe melting temperature of the ferrous metal to be cast, maintainingtheflame temperature and residence time of said particles in said flameat values to partially fused said particles, directing the stream ofpartially fused slag particles onto the walls of'a mold for adherencethereto and to each other to form a semi-porous lining of surfacebondedslag particles on the walls of the mold, pouring molten metal into theso-lined mold and allowing the heat of the molten metal to fuse the slaglining forming a shell of fluid casting slag between the metal body andthe walls of the mold, and solidifying the metal body. in themold-supported shell of casting slag.

10. Process for casting ferrous metal in a fluid slag casting moldcomprising directing a stream of particu lated casting slag materialthrough a flame, said slag material containing from about 15 to about 55percent by Weight silica and having a melting temperature less than themelting temperature of the ferrous metal to be cast, maintaining theflame temperature and residence time of said particles in said flame atvalues to partially fused said particles, directing the stream ofpartially fused slag particles onto the walls of a mold for adherencethereto and to each other to form a semi-porous lining of surface-bondedslag particles on the walls of the mold, pouring molten metal into theso-lined mold and allowing the heat oft he molten metal to fuse the slaglining forming a shell of fluid casting slag between the metal body andthe walls of the mold, and solidifying the metal body in the moldsupported shell of casting slag.

11. Process for casting alloys in a fluid slag casting mold comprisingdirecting a stream of particulated casting slag material through aflame, said casting slag containing a major proportion of lime andalumina and less than about 15 percent by weight silica and havingamelting temperature less than the melting temperature of the alloybeing cast, maintaining the flame temperature and residence time of saidparticles in said flame at values to partially fused said particles,directing the stream of partially fused slag particles onto the walls ofa mold for adherence thereto and to each other to form a semi-porouslining of surface-bonded slag particles on the walls of the mold,pouring molten metal into the so-lined mold and allowing the heat of themolten metal to fuse the slag lining forming a shell of fluid castingslag between the metal body and the walls of the mold, and solidifyingthe metal body in the mold-supported shell of casting slag.

12. Process for casting copper-containing metals in a fluid in a fluidslag casting mold comprising directing a stream of particulated castingslag material through a flame, said casting slag containing majorproportions of 'boric oxide and silica and being substantially inert tothe metal to be cast and having a melting temperature less than themelting temperature of the metal to be cast, maintaining the flametemperature and residence time of said particles in said flame at valuesto partially fused said particles, directing the stream of partiallyfused slag particles onto the walls of a mold for adherence thereto andto each other to form a semi-porous lining of surfacebonded slagparticles on the walls of the mold, pouring molten metal into theso-lined mold and allowing the heat of the molten metal to fuse the slaglining forming a shell of fluid casting slag between the metal body andthe Walls of the mold, and solidifying the metal body in themold-supported shell of casting slag.

References Cited by the Examiner UNITED STATES PATENTS 826,157

I. SPENCER OVERHOLSER, Primary Examiner.

WILLIAM J. STEPHENSON, Examiner.

1. PROCESS FOR CASTING METAL IN A FLUID SLAG CASTING MOLD COMPRISINGHEATING A STREAM OF PARTICULATED CASTING SLAG MATERIAL TO PARTIALLY FUSETHE SLAG PARTICLES AND DIRECTING THE STREAM OF PARTIALLY FUSED SLAG PARTICLES ONTO THE WALLS OF A MOLD FOR ADHERENCE TO THE MOLD WALLS AND TOEACH OTHER TO FORM A SEMI-POROUS LINING OF SURFACEBONDED SLAG PARTICLESON THE WALLS OF THE MOLD, POURING MOLTEN METAL INTO THE SO-LINED MOLDAND ALOWING THE